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src/java.base/share/classes/java/lang/ref/ReferenceQueue.java

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rev 12453 : [mq]: fix

*** 1,7 **** /* ! * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this --- 1,7 ---- /* ! * Copyright (c) 1997, 2015, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this
*** 61,74 **** ReferenceQueue<?> queue = r.queue; if ((queue == NULL) || (queue == ENQUEUED)) { return false; } assert queue == this; - r.queue = ENQUEUED; r.next = (head == null) ? r : head; head = r; queueLength++; if (r instanceof FinalReference) { sun.misc.VM.addFinalRefCount(1); } lock.notifyAll(); return true; --- 61,81 ---- ReferenceQueue<?> queue = r.queue; if ((queue == NULL) || (queue == ENQUEUED)) { return false; } assert queue == this; r.next = (head == null) ? r : head; head = r; queueLength++; + // Assignment of queue to special ENQUEUED queue must be + // after the reference is added to the queue's list. + // Otherwise, there is a race condition where the + // reference appears to be enqueued (isEnqueue returns + // true, another enqueue returns false), but polling the + // queue could find it still empty. The q.head and + // r.queue fields are volatile, ensuring that order. + r.queue = ENQUEUED; if (r instanceof FinalReference) { sun.misc.VM.addFinalRefCount(1); } lock.notifyAll(); return true;
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